U2687 – Vehicle Communication Bus Malfunction

The ODBII code U2687: Vehicle Communication Bus Malfunction indicates a problem with the communication between various control modules in the vehicle, which may affect their ability to exchange data properly.

The severity of ODBII code U2687 is moderate.

Common Causes For: U2685 U2685: Control Module Communication Bus Fault

• Faulty wiring or connectors in the communication bus
• Malfunctioning control modules
• Corrupted software or firmware in the modules
• Poor ground connections
• Interference from aftermarket devices
• Damaged or shorted communication lines
• Low battery voltage or power supply issues
• Faulty or damaged OBD-II port

Common misdiagnosis for U2687 U2687: Vehicle Communication Bus Malfunction

• Faulty Engine Control Module (ECM)
• Defective Body Control Module (BCM)
• Wiring issues or shorts in the communication bus
• Faulty sensors or actuators
• Issues with the powertrain control module (PCM)
• Corrupted software or firmware in modules
• Battery or charging system problems
• Grounding issues in the vehicle’s electrical system

Common Troubleshooting Steps

The OBD-II code U2687 indicates a “Vehicle Communication Bus Malfunction.” This code typically points to issues with the communication between various modules in the vehicle, often related to the CAN (Controller Area Network) bus system. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check for Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. Other codes can provide context and help identify the root cause of the problem.
• Inspect Wiring and Connectors: Visually inspect the wiring and connectors associated with the CAN bus. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors on the modules that are part of the communication network.
• Test the CAN Bus: Use a multimeter or an oscilloscope to check the voltage levels on the CAN bus wires. The typical voltage levels should be around 2.5V to 3.5V when the vehicle is on.
• Check for short circuits or open circuits in the CAN bus wiring.
• Check for Module Functionality: Identify the modules connected to the CAN bus and check if they are functioning properly. A malfunctioning module can disrupt communication.
• If possible, perform a module reset or reprogramming.
• Inspect Ground Connections: Ensure that all ground connections related to the modules and the CAN bus are secure and free of corrosion. Poor grounding can lead to communication issues.
• Look for Interference: Check for any aftermarket devices or modifications that may interfere with the CAN bus communication. This includes alarm systems, stereo systems, or other electronic devices.
• Perform a Network Test: Some advanced scan tools can perform a network test to check the integrity of the communication between modules. Use this feature if available.
• Check Battery Voltage: Ensure that the vehicle’s battery is in good condition and fully charged. Low voltage can affect module communication.
• Clear Codes and Test Drive: After performing the above checks and repairs, clear the trouble codes and take the vehicle for a test drive to see if the code returns.
• Consult Service Manual: Refer to the vehicle’s service manual for specific diagnostic procedures related to the CAN bus and the modules involved.1
• Seek Professional Help: If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific vehicle make and model. By following these troubleshooting steps, you can systematically identify and resolve the underlying issues causing the U2687 code.